Fluid power converter

ABSTRACT

A fluid power converter, such as a hydraulic fluid pump or motor, having a rotor and stator each having sealing vanes and in which the stator includes a contoured periphery consisting of harmonic curves which reduces rotor vane acceleration and provides a constant output source independent of rotational angle. The rotor periphery consisting of contoured curves shaped to impart harmonic motion to the stator vanes for reducing stator vane accelerations. The rotor and stator vanes having different thicknesses and provided with hydraulic and spring loading with the thicker vanes having a higer loading force thereby preventing destructive detenting of the vanes with respect to each other. Fluid timing plates for the rotor vanes sealing the hydraulic loading fluid in the rotor vane pockets during vane interaction periods for reducing wear and noise of the vane.

United States Patent m1 Gerlach et al.

1 Jan. 1,1974

[ FLUID POWER CONVERTER [75] Inventors: Charles R. Gerlach; Edgar C.

Schroeder, both of San Antonio,

[2]] App]. No.: 240,387

FOREIGN PATENTS OR APPLICATIONS Great Britain 418/221 1 PrimaryExaminerCar1ton R. Croyle Assistant Examiner-John J. VrablikAttorney-James F. Weller et a1.

[57] ABSTRACT A fluid power converter, such as a hydraulic fluid pump ormotor, having a rotor and stator each having sealing vanes and in whichthe stator includes a contoured periphery consisting of harmonic curveswhich reduces rotor vane acceleration and provides a constant outputsource independent of rotational angle. The rotor periphery consistingof contoured curves shaped to impart harmonic motion to the stator vanesfor reducing stator vane accelerations. The rotor and stator vaneshaving different thicknesses and provided with. heydrau is p, Qa n vi.th. he hic vanes having a higher loading force thereby preventingdestructive detenting of the vanes with respect to each other. Fluidtiming plates for the rotor vanes sealing the hydraulic loading fluid inthe rotor vane pockets during vane interaction periods for reducing wearand noise of the vane.

8 Claims, 2 Drawing Figures BACKGROUND OF THE INVENTION A hydraulicmotor and pump having vane elements on both the rotor and stator inwhich the contours of the stator and rotor are designed to provide aconstant net torque is shown in copending patent application Ser. No.883,692, entitled Fluid Power Converter", filed Dec. 10, 1969 now US.Pat. No. 3,622,797.

In the prior patent, the periphery contour causes excessive vaneacceleration forces for high speed operation because of the steep rampsbetween the recesses and the vanes. The present invention is directed toan improved fluid power converter in which the peripheries of the statorand/or the rotor, are contoured to not only provide a zero torquefluctuation or constant net torque, but overcome the problem ofexcessive vane acceleration forces during high speed operation. Inaddition, the present invention is directed to an improved fluid powerconverter in which various improvements are made in the vanes and vaneloading to avoid the destructive detenting of the stator and rotor vaneswith respect to each other.

SUMMARY One feature of the present invention is the provision of a fluidpower converter having a rotor and a stator which are concentricallymounted and rotatable one to the other end each of which have aperiphery including a plurality of equally spaced radially extendingslots for receiving a vane therein in which the stator contour includesa plurality of recesses defined by a harmonic curve having its centercoaxial with the common center and having an angular periphery extentsubstantially equal to 360 divided by the number of the stator vaneswhereby the stator contour will provide a constant torque design and yetavoid excessive rotor vane acceleration forces which occur at high speedoperations in stator designs having periphery contours with steep ramps.

Another feature of the present invention is a fluid power converter inwhich the rotor member has a contoured periphery having a plurality ofrecesses defined by a curve which is substantially harmonic forimparting harmonic motion to the stator vanes and thereby eliminatingexcessive stator vane acceleration forces having its center coaxial withthe common center and having an angular periphery extent substantiallyequal to 360 divided by the number of rotor vanes.

Another feature of the present fluid power converter is to reduce thedetenting action between the rotor and stator vanes by making the vanesin the stator of a different thickness than the vanes in the rotorwhereby the thicker vanes will not fit in the thinner slots and byloading the thicker vanes with a greater vane loading than the thinnervane so that the thinner vanes cannot detent into the thicker vane slotsbecause they do not have a sufficient force.

Yet a still further feature of the present invention is the provision ofa fluid converter in which both the rotor and stator vanes arehydraulically loaded with a high pressure fluid at all times but inwhich the fluid in place under the rotor vane is trapped or lockedduring the period the rotor and stator vanes cross each other therebylimiting the extent to which the rotor vanes can be displaced down intheir slots thereby reducing the tendency of the stator vanes to contactthe sharp corners of the rotor slot, prevent violent acceleration of therotor vanes down into their slots because of high speed interaction withthe stator vanes which causes excessive noise and loading of the rotorvane springs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic elevationalview, in cross section, showing the preferred embodiment of a rotor andstator of a fluid power converter according to the present invention,and

FIG. 2 is a schematic elevational view, in cross section, showing halfof one of the timing plates of the present invention and illustrating arotor with a modified contour.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings,and particularly to FIG. 1, the reference numeral 10 generally indicatesa fluid power converter, either gas or hydraulic, of the presentinvention. While either member of the converter 10 may be designed to bethe stator and the other the rotor, for purposes of illustration, member12 may be the stator and member 14 may be the rotor.

In order to obtain a theoretical constant torque design, it is necessaryto provide an even number of both rotor and stator vanes and there beingmore rotor vanes than stator vanes by at least two. The stator 12 isshown as including a plurality of radially extending valves receivingslots 22 for purposes of illustration only, here shown as four in numberequallv spaced around the stator 12 and each of which receives anysuitable type of valve element, here shown as self-pressurizing loadingvanes 24 therein whose outer ends 25 contact the outer periphery 18 ofthe rotor 14. The inner periphery 16 of the stator 12 and the outerperiphery 18 of the rotor 14 are suitably contoured, as will be morefully described hereinafter in detail, to provide an annular fluid space20 therebetween.

Similarly, the rotor 14 includes a plurality of equally spaced valveelement receiving slots 30, here shown as six for purposes ofillustration only, each of which receives a valve element such as a vane32 wherein the outer end 33 of which engages the inner periphery 16 ofthe stator 12. i

Fluid passageways 26 and 28 are provided on either side of the valveelements 24 in the stator 12 one of which, such as passageway 26 may bea fluid inlet and the other passageway, such as passageway 28, may be afluid outlet. Thus, assuming that the fluid power converter 12 is actingas a motor with the fluid coming in the fluid inlet passageways 26 andout of the fluid outlet passageways 28, the rotor 14 will rotatecounterclockwise relative to the stator 12.

In determining the proper contours of the periphery 16 and the stator 12and of the periphery 18 of the rotor 14, it is to be noted that aconstant torque output may be obtained so long as at least one of theperipheries 16 and 18 includes properly sized and shaped fluid recesses.However, in order to obtain maximum fluid displacement and thus maximumoutput for a given size, it is desirable that both peripheries 16 and 18include working recesses.

In the particular illustration shown in FIG. 1, utilizing six vanes 32on the rotor 14 and four vanes 24 on' the rotor 12, the stator containsfour contoured recesses 40.

tendible stator vanes 24 which seal against the rotor periphery 18. Therotor contains six contoured recesses 50 of nominally 60 angular extent,separated by six extendible rotor vanes 32 which seal against the statorperiphery 16. The stator and rotor periphery contours are designed toalways provide a theoretically perfect or constant output torque,independent of rotational angles.

Of course, the rotor and stator contour as described in US. Pat. No.3,622,797, also provided a theoretical constant output torque, but inthat design the vanes were required to move across relatively steepramps and cause excessive vane acceleration forces at high speedoperation which is undesirable. In one embodiment of the presentapparatus 10, each of the stator recesses 40 is of a harmonic design.Thus, each of the recesses 40 is defined by a harmonic curve 42 havingits center coaxial with said common center and having an angularperiphery extent substantially equal to 360 divided by the number of thestator vanes. The displacement of the harmonic curves 42 from the pitchdiameter for the maximum diameter of rotor 14 equals (Ax)/2 (l cos 4 6),where Ax is the maximum displacement and is 360. the stator 12 by havingthe harmonic curves 42, discounting the rotor vane widths, is a constanttorque design by virtue of providing an equal sum total displacement forall working rotor vanes 32 as they move around the periphery 16 of thestator 12.

Similarly, the rotor recesses 50 are each defined by a curve 52 which isnominally a harmonic curve having its center coaxial with said commoncenter and having an angular periphery extent substantially equal to 360divided by the number of rotor vanes. In practice, the rotor contour 52may be slightly modified to account for the effect ofa finite vane widthso that the resultant contour imparts a harmonic motion to the statorvanes. Theoretical harmonic curves 52 on the rotor 14, discounting thefinite width of the stator vanes 24, would provide a constant sum totaldisplacement for the four stator vanes 24 and the stator vanes 24working or sealing against the harmonic contoured rotor-14 provide aconstant output torque. Taking into account the finite stator vane widththe sum total displacement of the stator vanes is not precisely constantthere being a small error because the vanes do not experience harmonicmotion, even though the rotor surface is ofa harmonic design. Therefore,this slight error may be corrected by modifying the rotor contour 52 toimpart harmonic motion to the stator vanes, but the contour 52 willstill be substantially harmonic. The design of the harmonic contouredstator 12 and the substantially harmonic contoured rotor 14, whilesacrificing some amount of displacement, provides a superior high speedperformance.

As previously mentioned, in order to obtain maximum fluid displacementand thus maximum output for a given size apparatus 10, it is desirablethat both peripheries l6 and 18 include working recesses. However, ifdesired, the working recesses may be omitted from either the stator 12or the rotor 14. As best seen in FIG. 2, the recesses 50 have beenomitted from the rotor 14 and the periphery 18a thereof is merely acircle of constant radius. Similarly, and not shown, the recesses 40 inthe stator 12 may be omitted and the periphery 18 may be circular.

Another problem in general encountered in fluid power converters havingvanes in both the rotor and stator is the interaction between the vaneson the rotor with the vanes on the stator. That is, as the rotor andstator rotate relative to each other the vanes on the rotor will crossthe vanes on the stator and cause excessive noise and destructivedetenting of the vanes one with respect to the other. Another feature ofthe present invention is the improved design of the stator and the rotorvanes and loading means for the vanes. While a fluid converter 10 can beinitially manufactured wherein the rotor vanes 32 and the stator vanes24 are precisely as tall as their respective slots 30 and 22, and thusinitially prevent the rotor vanes 24 from catching in the stator slots22 and preventing the stator vanes 24 from catching in the rotor slots30. However, subsequent wear may permit the vanes 32 on the rotor 18 toextend into the stator slots 22 or the stator vanes 24 to extend overinto rotor slots 30 causing undesirable noise and damage. To preventthis occurrence, the vanes on either the stator 12 or the rotor 14 aremade thicker than the vanes on the other member. For example, andreferring to FIG. 1, the stator vanes 24 are thicker, preferably about30 percent, than the rotor vanes 32. Thus, the stator vanes 24 cannotdetent into rotor slots 30 because the vanes 24 are too wide. Inaddition, the loading on the back of the stator vanes 24 may be madehigher than the loading on the back of the rotor vanes 32 so that thesmaller rotor vanes 32 cannot detent into a larger slot 22 because theloading force on the rotor vanes 32 will be less than the loading forceon the stator vanes 24. The loading on the back of the stator vanes 24may be conventionally accomplished by providing high pressure hydraulicfluid in the slots 22 acting against the back of the stator vanes 24from the high pressure supply ports 26 or a separate supply and- /orsprings 54. Obviously, if the hydraulic fluid used for loading thestator vanes 24 and the rotor vanes 32 is from the same supply theloading force on the stator vanes 22 will be greater than the loadingforce on the rotor vanes 32 because of the greater thickness of thestator vanes 24. Of course, if the loading on the vanes 24 and 32 isaccomplished solely by springs 54 and 64, respectively, the stator vanespring 54 are provided with a higher resilient force than the rotor vanesprings 64 in order to insure that the rotor vanes 34 do not detent intoa stator slots 22. Preferably, the loading is accomplished by bothhydraulic loading and spring loading. An additional benefit of theforegoing structure is that the manufacturing tolerances on the vaneheights and slot depths may be increased since neither the stator vanes24 or the rotor vanes 32 need be the full depth of the slots 22 and 30,respectively.

Ideally, both the rotor vanes 32 and the stator vanes 24 arehydraulically loaded with high pressure of supply fluid at all times, orfor all rotational angles. In practice under such conditions, however,it has been found that the stator vanes 24 because of their greaterloading slap down the lighter loaded stator vanes 32 causing noise andexcessive loading of the rotor vane springs 64 and at low speeds permitsthe stator vanes 24 to scrape across the sharp edges of the rotor slots30. That is, the higher loaded stator vanes 24 will overcome the lowerloaded rotor vanes 32 and push the rotor vanes 32 inwardly overcomingthe hydraulic and spring loading of the rotor vanes 32.

Therefore, another feature of the present invention is the provision ofmeans for locking or trapping the hydraulic loading fluid in placebehind the rotor vanes 32 to create a hydraulic lock in the rotor slots30 when the stator vanes 24 and the rotor vanes 34 interact so that therotor vanes 32 cannot be pushed down by the stator vanes 24. Suitablemeans to trap or lock the fluid in place under the rotor vanes areprovided such as a timing plate 70, preferably, on each end of the rotor14. The timing plate 70 includes a plurality of openings 72 which supplyhigh pressure oil through the end plate 70 to a fluid pocket 74 behindeach rotor vane 32. The openings 72 are positioned and the pocket 74 aresized so that high pressure oil is supplied to the rotor vanes 32 whilethey are operating on the stator contours between points A and B. Highpressure oil is supplied to the opposing or back side of each timingplate 70 using an appropriate annulus supplied by a check valve system(not shown) which permits high pressure, but not low pressure to enter.Such a check valve system is required only for reversible motors andpumps.

However, it is noted that the timing plates 70 are stationary and thatthe openings 72 are positioned so that when a moving rotor vane 32approaches a stator vane 24 the fluid pocket 74 rotates out ofcommunication with the openings 72 thereby sealing the fluid in thepockets 74 so that loading fluid can neither enter nor leave the pockets74 as the rotor vane 32 travels from point B to point C. Thus, duringthe period when the rotor and stator vanes must interact or pass overeach other, the hydraulic loading fluid beneath the rotor vanes 32 iscreating a hydraulic block so that the rotor vanes 32 cannot beviolently pushed down by the stator vanes 24.

lt is also noted that because of normal wear on the rotor and statorvane tips, they become slightly curved on the ends. Hence, it isdifficult to avoid a slight tendency for the more heavily loaded statorvanes 24 to protrude slightly into the rotor slots 30 during theinteraction period unless opposed in some manner. The above describedrotor fluid trapping structure provides a means which also avoids thisproblem.

Thus, the present invention provides a periphery contour to a statorand/or a rotor of a harmonic curve which achieves an idea] ortheoretical constant torque operation for all rotational angles of therotor. In addition, the rotor periphery may be modified slightly toimpart a harmonic motion to the stator vanes for reducing vaneacceleration for improved high speed operation. The destructivedetenting of the vanes of the rotor relative to the vanes of the statorare reduced by providing the rotor and stator vanes With a differingthickness whereby the thicker vanes cannot enter the narrower slot ofthe other member and by providing greater loading on the thicker vanesto prevent the thinner vanes from moving into the wider slots of thethicker vanes. The timing plates for the rotor vanes loading seal thehydraulic loading fluid in the rotor vane pockets during the vaneinteraction period which prevents caming or slapping action of thestator vanes against the rotor vanes to cause the motor vanes to bebounced down into their slots.

The present invention, therefore, is well adapted to carry out theobjects and attain the ends and advantages mentioned as well as othersinherent therein. While presently preferred embodiments of the inventionare given for the purpose of disclosure, numerous changes in the detailsof construction and arrangement of parts will readily suggest themselvesto those skilled in the art and which are encompassed within the spiritof the invention and the scope of the appended claims.

What is claimed is:

1. in a fluid power converter having a rotor and a stator member, themembers being concentrically mounted and rotatable one with respect tothe other about a common center, said members having opposingperipheries contoured to provide an annular space therebetween, each ofsaid peripheries including a plurality of equispaced radially extendingslots receiving a vane therein, there being an even number of both rotorand stator vanes and there being more rotor vanes than stator vanes, afluid inlet in the stator adjacent one side of each slot therein andopening into the annular space, a fluid outlet in the stator adjacentthe second side of each slot therin and opening into the annular space,the improvement comprising,

the stator periphery including a plurality of recesses each of which isdefined by a harmonic curve having its center coaxial with said commoncenter and having an angular periphery extent substantially equal to 360divided by the number of stator vanes, and

the rotor periphery includes a plurality of recesses each of which isdefined by a curve which is substantially harmonic for impartingharmonic motion to the stator vanes and having its center coaxial withsaid common center and having an angular periphery extent substantiallyequal to 360 divided by the number of rotor vanes thereby reducing vaneacceleration and providing a constant torque converter.

2. The apparatus of claim 1 including,

means for supplying hydraulic fluid on the back of said rotor and statorvanes, and

means for locking the hydraulic fluid on the vanes in one of the rotorand stator in place during the time the rotor and stator vanes crosseach other for preventing escape of fluid from the back of the lockedvanes.

3. The apparatus of claim 1 including,

the vanes in the stator being of a different thickness than the vanes inthe rotor,

means for urging the stator and the rotor vanes out wardly from thestator and rotor, respectively, and

said means urging the vanes outwardly providing a greater force on thegreater thickness vanes.

4. The apparatus of claim 6 wherein the means urging the stator androtor vanes outwardly being springs, and

the springs urging the greater thickness vanes outwardly having a higherforce than the springs urging the lesser thickness vanes outwardly.

5. In a hydraulic power converter having a rotor and a stator member,the members being concentrically mounted and rotatable one with respectto the other about a common center, said members having opposingperipheries contoured to provide an annular space therebetween, each ofsaid peripheries including a plurality of equispaced radially extendingslots receiving a vane therein, a fluid inlet in the stator adjacent oneside of each slot therein and opening into the annular space, a fluidoutlet in the stator adjacent thesecond side of each slot therein andopening into the annular space, the improvement comprising,

hydraulic fluid applied against the back of the stator vanes and therotor vanes for urging the stator vanes and the rotor vanes outwardlyfrom the stator and rotor, respectively, and

locking means for preventing escape of fluid from the back of the vanesthereby sealing the hydraulic fluid acting on the vanes in one of therotor and stator in place during the time the rotor and stator vanescross each other thereby preventing the locked vanes from being pushedinto their slots by the other vanes.

6. The apparatus of claim wherein,

the vanes in the stator being of a different thickness than the vanes inthe rotor,

means for urging the stator and the rotor vanes outwardly from thestator and rotor, respectively,

said means urging the vanes outwardly providing a greater force on thegreater thickness vanes, and

said means for urging the stator and rotor vanes outwardly includes,

hydraulic fluid applied against the back of the vanes, and

also includes springs applied against the back of the vanes, the springsurging the greater thickness vanes outwardly having a greater force thanthe springs urging the lesser thickness vanes outwardly.

7. The apparatus of claim 5 wherein the vanes in the stator being of adifferent thickness than the vanes in the rotor, and wherein the lockingmeans act on the thinner vanes.

8. The apparatus of claim 7 wherein the thinner vanes are the rotorvanes and wherein the hydraulic locking means includes a plate on bothends of the rotor having timing ports, said ports positioned between theback of the rotor vanes and high pressure hydraulic fluid, and saidports normally open but being closed during the time when the rotor andstator vanes cross each other.

1. In a fluid power converter having a rotor and a stator member, themembers being concentrically mounted and rotatable one with respect tothe other about a common center, said members having opposingperipheries contoured to provide an annular space therebetween, each ofsaid peripheries including a plurality of equispaced radially extendingslots receiving a vane therein, there being an even number of both rotorand stator vanes and there being more rotor vanes than stator vanes, afluid inlet in the stator adjacent one side of each slot therein andopening into the annular space, a fluid outlet in the stator adjacentthe second side of each slot therin and opening into the annular space,the improvement comprising, the stator periphery including a pluralityof recesses each of which is defined by a harmonic curve having itscenter coaxial with said common center and having an angular periphEryextent substantially equal to 360* divided by the number of statorvanes, and the rotor periphery includes a plurality of recesses each ofwhich is defined by a curve which is substantially harmonic forimparting harmonic motion to the stator vanes and having its centercoaxial with said common center and having an angular periphery extentsubstantially equal to 360* divided by the number of rotor vanes therebyreducing vane acceleration and providing a constant torque converter. 2.The apparatus of claim 1 including, means for supplying hydraulic fluidon the back of said rotor and stator vanes, and means for locking thehydraulic fluid on the vanes in one of the rotor and stator in placeduring the time the rotor and stator vanes cross each other forpreventing escape of fluid from the back of the locked vanes.
 3. Theapparatus of claim 1 including, the vanes in the stator being of adifferent thickness than the vanes in the rotor, means for urging thestator and the rotor vanes outwardly from the stator and rotor,respectively, and said means urging the vanes outwardly providing agreater force on the greater thickness vanes.
 4. The apparatus of claim6 wherein the means urging the stator and rotor vanes outwardly beingsprings, and the springs urging the greater thickness vanes outwardlyhaving a higher force than the springs urging the lesser thickness vanesoutwardly.
 5. In a hydraulic power converter having a rotor and a statormember, the members being concentrically mounted and rotatable one withrespect to the other about a common center, said members having opposingperipheries contoured to provide an annular space therebetween, each ofsaid peripheries including a plurality of equispaced radially extendingslots receiving a vane therein, a fluid inlet in the stator adjacent oneside of each slot therein and opening into the annular space, a fluidoutlet in the stator adjacent the second side of each slot therein andopening into the annular space, the improvement comprising, hydraulicfluid applied against the back of the stator vanes and the rotor vanesfor urging the stator vanes and the rotor vanes outwardly from thestator and rotor, respectively, and locking means for preventing escapeof fluid from the back of the vanes thereby sealing the hydraulic fluidacting on the vanes in one of the rotor and stator in place during thetime the rotor and stator vanes cross each other thereby preventing thelocked vanes from being pushed into their slots by the other vanes. 6.The apparatus of claim 5 wherein, the vanes in the stator being of adifferent thickness than the vanes in the rotor, means for urging thestator and the rotor vanes outwardly from the stator and rotor,respectively, said means urging the vanes outwardly providing a greaterforce on the greater thickness vanes, and said means for urging thestator and rotor vanes outwardly includes, hydraulic fluid appliedagainst the back of the vanes, and also includes springs applied againstthe back of the vanes, the springs urging the greater thickness vanesoutwardly having a greater force than the springs urging the lesserthickness vanes outwardly.
 7. The apparatus of claim 5 wherein the vanesin the stator being of a different thickness than the vanes in therotor, and wherein the locking means act on the thinner vanes.
 8. Theapparatus of claim 7 wherein the thinner vanes are the rotor vanes andwherein the hydraulic locking means includes a plate on both ends of therotor having timing ports, said ports positioned between the back of therotor vanes and high pressure hydraulic fluid, and said ports normallyopen but being closed during the time when the rotor and stator vanescross each other.